Looking for Lisa, whose sister Cyndi died and father is Michael Gandy

Lisa and Cyndi are apparently my half-sisters that I have never met. I was told that Cyndi was murdered in South Carolina in 1991? My bio-dad is Michael Dalton Gandy born in 1941. He had four children including myself with three different women. David Gandy is my half-brother, who has a son named Christopher Gandy. Our bio-dad abandoned me, and supposedly his other kids, too. I am looking to find Lisa or anybody who knows of them in hopes I can learn about my family from that side.

Other family details include my aunts Linda Annette Nettles and Rebecca Jean May. Grandparents Dalton Gandy and Tommie Evelyn Billingsley Gandy. My bio-dad was previously married to Patsy Ann Page Gandy (no kids?), Jane Louise Gandy (mother of David), and an unknown woman who is likely Cyndi and Lisa's mother. I was born in 1983 by Shannon. My bio-dad later married Maria Gandy that I know nothing about. Also had a girlfriend of five years whom I can't remember the name of. She contacted me about 5-6 years ago very briefly and I lost her info. Darlene? Or Darla? Or maybe Debbie?

I discovered Patsy died 31 days after she and my bio-dad divorced (1978), but I'm trying to find out how she died. Anybody?